CLINICAL PHARMACOLOGY
Mechanism Of Action
Prior to rotavirus vaccination programs, rotavirus
infected nearly all children by the time they were 5 years of age. Severe,
dehydrating rotavirus gastroenteritis occurs primarily among children aged 3 to
35 months.6 Among children up to 3 years of age, approximately 16%
of cases before 6 months of age result in hospitalization.7
The exact immunologic mechanism by which ROTARIX protects
against rotavirus gastroenteritis is unknown [see Pharmacodynamics].
ROTARIX contains a live, attenuated human rotavirus that replicates in the
small intestine and induces immunity.
Pharmacodynamics
Immunogenicity
 A relationship between antibody responses to rotavirus
vaccination and protection against rotavirus gastroenteritis has not been
established. Seroconversion was defined as the appearance of anti-rotavirus IgA
antibodies (concentration ≥ 20 U/mL) postvaccination in the serum of
infants previously negative for rotavirus. In 2 safety and efficacy studies,
one to two months after a 2-dose series, 86.5% of 787 recipients of ROTARIX seroconverted
compared with 6.7% of 420 placebo recipients and 76.8% of 393 recipients of ROTARIX
seroconverted compared with 9.7% of 341 placebo recipients, respectively.
Shedding and Transmission
A prospective, randomized, double-blind, placebo-controlled
study was performed in the Dominican Republic in twins within the same
household to assess whether transmission of vaccine virus occurs from a
vaccinated infant to a nonvaccinated infant. One hundred pairs of healthy twins
6 to 14 weeks of age (gestational age ≥ 32 weeks) were randomized with one
twin to receive ROTARIX (N = 100) and the other twin to receive placebo (N =
100). Twenty subjects in each arm were excluded for reasons such as having
rotavirus antibody at baseline. Stool samples were collected on the day of or 1
day prior to each dose, as well as 3 times weekly for 6 consecutive weeks after
each dose of ROTARIX or placebo. Transmission was defined as presence of the
vaccine virus strain in any stool sample from a twin receiving placebo.
Transmitted vaccine virus was identified in 15 of 80
twins receiving placebo (18.8% [95% CI: 10.9, 29.0]). Median duration of the
rotavirus shedding was 10 days in twins who received ROTARIX as compared to 4
days in twins who received placebo in whom the vaccine virus was transmitted.
In the 15 twins who received placebo, no gastrointestinal symptoms related to
transmitted vaccine virus were observed.
Clinical Studies
Efficacy Studies
The data demonstrating the efficacy of ROTARIX in
preventing rotavirus gastroenteritis come from 24,163 infants randomized in two
placebo-controlled studies conducted in 17 countries in Europe and Latin
America. In these studies, oral polio vaccine (OPV) was not coadministered;
however, other routine childhood vaccines could be concomitantly administered. Breast-feeding
was permitted in both studies.
A randomized, double-blind, placebo-controlled study was
conducted in 6 European countries. A total of 3,994 infants were enrolled to
receive ROTARIX (n = 2,646) or placebo (n = 1,348). Vaccine or placebo was
given to healthy infants as a 2-dose series with the first dose administered
orally from 6 through 14 weeks of age followed by one additional dose administered
at least 4 weeks after the first dose. The 2-dose series was completed by 24
weeks of age. For both vaccination groups, 98.3% of infants were white and 53%
were male.
The clinical case definition of rotavirus gastroenteritis
was an episode of diarrhea (passage of 3 or more loose or watery stools within
a day), with or without vomiting, where rotavirus was identified in a stool
sample. Severity of gastroenteritis was determined by a clinical scoring
system, the Vesikari scale, assessing the duration and intensity of diarrhea
and vomiting, the intensity of fever, use of rehydration therapy or
hospitalization for each episode. Scores range from 0 to 20, where higher
scores indicate greater severity. An episode of gastroenteritis with a score of
11 or greater was considered severe.8
The primary efficacy endpoint was prevention of any grade
of severity of rotavirus gastroenteritis caused by naturally occurring
rotavirus from 2 weeks after the second dose through one rotavirus season
(according to protocol, ATP). Other efficacy evaluations included prevention of
severe rotavirus gastroenteritis, as defined by the Vesikari scale, and
reductions in hospitalizations due to rotavirus gastroenteritis and all cause
gastroenteritis regardless of presumed etiology. Analyses were also done to
evaluate the efficacy of ROTARIX against rotavirus gastroenteritis among
infants who received at least one vaccination (total vaccinated cohort, TVC).
Efficacy of ROTARIX against any grade of severity of
rotavirus gastroenteritis through one rotavirus season was 87.1% (95% CI: 79.6,
92.1); TVC efficacy was 87.3% (95% CI: 80.3, 92.0). Efficacy against severe
rotavirus gastroenteritis through one rotavirus season was 95.8% (95% CI: 89.6,
98.7); TVC efficacy was 96.0% (95% CI: 90.2, 98.8) (Table 4). The protective effect
of ROTARIX against any grade of severity of rotavirus gastroenteritis observed immediately
following dose 1 administration and prior to dose 2 was 89.8% (95% CI: 8.9,
99.8).
Efficacy of ROTARIX in reducing hospitalizations for
rotavirus gastroenteritis through one rotavirus season was 100% (95% CI: 81.8,
100); TVC efficacy was 100% (95% CI: 81.7, 100) (Table 4). ROTARIX reduced
hospitalizations for all cause gastroenteritis regardless of presumed etiology
by 74.7% (95% CI: 45.5, 88.9).
Table 4: Efficacy Evaluation of ROTARIX Through One
Rotavirus Season
Infants in Cohort |
According to Protocola |
Total Vaccinated Cohortb |
ROTARIX
N = 2,572 |
Placebo
N = 1,302 |
ROTARIX
N = 2,646 |
Placebo
N = 1,348 |
Gastroenteritis cases |
Any severity |
24 |
94 |
26 |
104 |
Severec |
5 |
60 |
5 |
64 |
Efficacy estimate against RV GE |
Any severity (95% CI) |
87.1%d (79.6, 92.1) |
87.3%d (80.3, 92.0) |
Severec (95% CI) |
95.8%d (89.6, 98.7) |
96.0%d (90.2, 98.8) |
Cases of hospitalization due to RV GE |
0 |
12 |
0 |
12 |
Efficacy in reducing hospitalizations due to RV GE (95% CI) |
100%d (81.8, 100) |
100%d (81.7, 100) |
RV GE = rotavirus gastroenteritis; CI = Confidence
Interval.
a ATP analysis includes all infants in the efficacy cohort who
received two doses of vaccine according to randomization.
b TVC analysis includes all infants in the efficacy cohort who
received at least one dose of vaccine or placebo.
c Severe gastroenteritis defined as ≥ 11 on the Vesikari scale.
DStatistically significant vs. placebo (P < 0.001). |
A randomized, double-blind, placebo-controlled study was
conducted in 11 countries in Latin America and Finland. A total of 63,225
infants received ROTARIX (n = 31,673) or placebo (n = 31,552). An efficacy
subset of these infants consisting of 20,169 infants from Latin America
received ROTARIX (n = 10,159) or placebo (n = 10,010). Vaccine or placebo was given
to healthy infants as a 2-dose series with the first dose administered orally
from 6 through 13 weeks of age followed by one additional dose administered at
least 4 weeks after the first dose. The 2-dose series was completed by the age
of 24 weeks of age. For both vaccination groups, the racial distribution of the
efficacy subset was as follows: Hispanic 85.8%, white 7.9%, black 1.1%, and
other 5.2%; 51% were male.
The clinical case definition of severe rotavirus
gastroenteritis was an episode of diarrhea (passage of 3 or more loose or
watery stools within a day), with or without vomiting, where rotavirus was
identified in a stool sample, requiring hospitalization and/or rehydration
therapy equivalent to World Health Organization (WHO) plan B (oral rehydration
therapy) or plan C (intravenous rehydration therapy) in a medical facility.
The primary efficacy endpoint was prevention of severe
rotavirus gastroenteritis caused by naturally occurring rotavirus from 2 weeks
after the second dose through one year (ATP). Analyses were done to evaluate
the efficacy of ROTARIX against severe rotavirus gastroenteritis among infants
who received at least one vaccination (TVC). Reduction in hospitalizations due
to rotavirus gastroenteritis was also evaluated (ATP).
Efficacy of ROTARIX against severe rotavirus
gastroenteritis through one year was 84.7% (95% CI: 71.7, 92.4); TVC efficacy
was 81.1% (95% CI: 68.5, 89.3) (Table 5).
Efficacy of ROTARIX in reducing hospitalizations for
rotavirus gastroenteritis through one year was 85.0% (95% CI: 69.6, 93.5); TVC
efficacy was 80.8% (95% CI: 65.7, 90.0) (Table 5).
Table 5: Efficacy Evaluation of ROTARIX Through One
Year
Infants in Cohort |
According to Protocola |
Total Vaccinated Cohortb |
ROTARIX
N = 9,009 |
Placebo
N = 8,858 |
ROTARIX
N = 10,159 |
Placebo
N = 10,010 |
Gastroenteritis cases |
Severe |
12 |
77 |
18 |
94 |
Efficacy estimate against RV GE |
Severe (95% CI) |
84.7%c (71.7, 92.4) |
81.1 %c (68.5, 89.3) |
Cases of hospitalization due to RV GE |
9 |
59 |
14 |
72 |
Efficacy in reducing hospitalizations due to RV GE (95% CI) |
85.0%c (69.6, 93.5) |
80.8%c (65.7, 90.0) |
RV GE = rotavirus gastroenteritis; CI = Confidence
Interval.
a ATP analysis includes all infants in the efficacy cohort who
received two doses of vaccine according to randomization.
bTVC analysis includes all infants in the efficacy cohort who
received at least one dose of vaccine or placebo.
c Statistically significant vs. placebo (P < 0.001). |
Efficacy Through Two Rotavirus Seasons
The efficacy of ROTARIX persisting through two rotavirus
seasons was evaluated in two studies.
In the European study, the efficacy of ROTARIX against
any grade of severity of rotavirus gastroenteritis through two rotavirus
seasons was 78.9% (95% CI: 72.7, 83.8). Efficacy in preventing any grade of
severity of rotavirus gastroenteritis cases occurring only during the second
season post-vaccination was 71.9% (95% CI: 61.2, 79.8). The efficacy of ROTARIX
against severe rotavirus gastroenteritis through two rotavirus seasons was
90.4% (95% CI: 85.1, 94.1). Efficacy in preventing severe rotavirus
gastroenteritis cases occurring only during the second season post-vaccination
was 85.6% (95% CI: 75.8, 91.9).
The efficacy of ROTARIX in reducing hospitalizations for
rotavirus gastroenteritis through two rotavirus seasons was 96.0% (95% CI:
83.8, 99.5).
In the Latin American study, the efficacy of ROTARIX
against severe rotavirus gastroenteritis through two years was 80.5% (95% CI:
71.3, 87.1). Efficacy in preventing severe rotavirus gastroenteritis cases
occurring only during the second year post-vaccination was 79.0% (95% CI: 66.4,
87.4). The efficacy of ROTARIX in reducing hospitalizations for rotavirus gastroenteritis
through two years was 83.0% (95% CI: 73.1, 89.7).
The efficacy of ROTARIX beyond the second season
post-vaccination was not evaluated.
Efficacy Against Specific Rotavirus Types
The type-specific efficacy against any grade of severity
and severe rotavirus gastroenteritis caused by G1P[8], G3P[8], G4P[8], G9P[8],
and combined non-G1 (G2, G3, G4, G9) types was statistically significant
through one year. Additionally, type-specific efficacy against any grade of
severity and severe rotavirus gastroenteritis caused by G1P[8], G2P[4], G3P[8],
G4P[8], G9P[8], and combined non-G1 (G2, G3, G4, G9) types was statistically significant
through two years (Table 6).
Table 6: Type-Specific Efficacy of ROTARIX Against Any
Grade of Severity and Severe Rotavirus Gastroenteritis (According to Protocol)
Type Identifieda |
Through One Rotavirus Season |
Through Two Rotavirus Seasons |
Number of Cases |
% Efficacy (95% CI) |
Number of Cases |
% Efficacy (95% CI) |
ROTARIX
N = 2,572 |
Placebo
N = 1,302 |
ROTARIX
N = 2,572 |
Placebo
N = 1,302 |
ANY GRADE OF SEVERITY |
G1P[8] |
4 |
46 |
95.6%b (87.9, 98.8) |
18 |
89c,d |
89.8%b
(82.9, 94.2) |
G2P[4] |
3 |
4c |
NS |
14 |
17c |
58.3%b
(10.1, 81.0) |
G3P[8] |
1 |
5 |
89.9%b (9.5, 99.8) |
3 |
10 |
84.8%b (41.0, 97.3) |
G4P[8] |
3 |
13 |
88.3%b (57.5, 97.9) |
6 |
18 |
83.1%b (55.6, 94.5) |
G9P[8] |
13 |
27 |
75.6%b (51.1, 88.5) |
38 |
71d |
72.9%b
(59.3, 82.2) |
Combined non-G1 (G2, G3, G4, G9, G12) typese |
20 |
49 |
79.3%b (64.6, 88.4) |
62 |
116 |
72.9%b (62.9, 80.5) |
SEVERE |
G1P[8] |
2 |
28 |
96.4%b (85.7, 99.6) |
4 |
57 |
96.4%b
(90.4, 99.1) |
G2P[4] |
1 |
2c |
NS |
2 |
7c |
85.5%b
(24.0, 98.5) |
G3P[8] |
0 |
5 |
100%b
(44.8, 100) |
1 |
8 |
93.7%b
(52.8, 99.9) |
G4P[8] |
0 |
7 |
100%b
(64.9, 100) |
1 |
11 |
95.4%b
(68.3, 99.9) |
G9P[8] |
2 |
19 |
94.7%b
(77.9, 99.4) |
13 |
44d |
85.0%b (71.7, 92.6) |
Combined non-G1 (G2, G3, G4, G9, G12) typese |
3 |
33 |
95.4%b
(85.3, 99.1) |
17 |
70 |
87.7%b (78.9, 93.2) |
CI = Confidence Interval; NS = Not significant.
a Statistical analyses done by G type; if more than one rotavirus
type was detected from a rotavirus gastroenteritis episode, the episode was
counted in each of the detected rotavirus type categories.
b Statistically significant vs. placebo (P < 0.05).
c The P genotype was not typeable for one episode.
d P[8] genotype was not detected in one episode.
e Two cases of G12P[8] were isolated in the second season (one in
each group). |
REFERENCES
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6. Centers for Disease Control and Prevention. Prevention
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